1. Technical Field
The disclosure is generally related to an auto-focusing lens including a liquid zooming unit. More particularly, the liquid zooming unit can have controlled zooming that can be applicable in a camera.
2. Description of Related Art
Conventionally, an interface for a liquid lens is formed by using two mutually dissoluble liquids, such as water and oil, in which the liquids have similar densities to each other. Due to electrowetting effects, when a suitable voltage is applied on the side walls confining the two liquids, generating an electric field, the curvature of the interface is altered, thereby changing the optical power of the interface and achieving similar focusing effects to mechanically displaced lenses. Due to the ease of curvature change, it has become advantageous to use the liquid lens as a zooming unit.
Lens groups utilizing liquid lenses have been previously disclosed. For example, disclosures in U.S. Publication No. 2006/0056042 and 2007/0229970 have suggested liquid lenses capable of zooming functions. However, for the liquid lenses described in the two disclosures, sequence of the refractive indices of the two liquids are restricted, and the whole lense group has large overall thicknesses.
Lens sizes have been in a trend toward miniaturization. Conventional auto-focusing optical lenses require movable lenses and movable space, therefore decreasing lens volume has been difficult. Moreover, since conventional auto-focusing optical lenses also require mechanical parts for the movable lenses, more power consumption and space requirements are needed, thereby complicating efforts toward miniaturization. In addition, because the range of object distances for photo taking is restricted from infinity to 10 cm, picture quality of close-up shots is poorer and auto-focus speed is slower. Furthermore, such conventional lenses require back optical power adjustments, but optical components capable of complex movements may be fragile and unreliable.